A number of different aspects of membrane transport mechanisms in mitochondria will be examined. Ca2 ion transport across the mitochondrial membrane will be examined with particular reference to the membrane binding sites to which Ca2 ion must attach before it is transported. Since binding of Ca2 ion to the energized sites is extremely rapid, special methods will be required to measure the kinetics of Ca2 ion binding and H ion release. The kinetics of energized Ca2 ion binding will be evaluated in connection with the possible role of mitochondria in segregation of Ca2 ion during contraction-relaxation cycles of heart muscle. The role of mitochondria in biological calcification will also be examined in the hepatopancrease of the blue crab during the extensive salvage of Ca2 ion and Pi prior to moulting, as a model for calcification in vertebrates. Crab liver mitochondria have an enormous capacity for transporting Ca2 ion,and form very large electron dense but non-crystalline deposits of calcium phosphate; we shall examine them for substances inhibitory to hydroxyapatite formation. Also to be studied are the dynamics of Ca2 ion transport by intact Ehrlich ascites tumor cells, as well as by tumor mitochondria, which have an especially great capacity for retaining Ca2 ion. In other studies the solubilized ATP-ADP carrier of the inner mitochondrial membrane is to be purified.